A 71-year-old man who lived alone in his Bronx apartment died there in an early-morning fire yesterday, officials said.

Neighbors identified the man as Rafael Lind, a quiet, sickly man who for several years had seldom left his ninth-floor apartment at Concourse Village, 31-35 Park Ave., in the Morris Heights section.

Officials said the flames were contained within the apartment walls, and neighbors said they didn't know about the fire until they noticed a full squadron of firefighters rushing in at about 1:45 a.m. Fifty firefighters in 12 units extinguished the fire in about half an hour.

A police source said Lind was found dead in his bathroom.

"He was a quiet person, very tranquil, and he died that way," said neighbor Flora Perez, who is also 71. She said Lind had lived in the building for at least 15 years. "He hardly spoke to me, and he was my neighbor."

She said Lind's wife died several years ago. She did not know of any other immediate family.

Perez said Lind walked with a cane or a walker and had become increasingly senile in recent years. "No one knew he was in there, because he never left except to go to the doctor's with his attendant," she said.

Yesterday, Lind's door was padlocked.

The cause of the fire is under investigation, but an official said it appears to have been accidental.